Re: [PATCH] net/mlx5e: always initialize frag->last_in_page

[Tariq Toukan <tariqt@mellanox.com>]

On 7/31/2019 10:02 PM, Qian Cai wrote:
> The commit 069d11465a80 ("net/mlx5e: RX, Enhance legacy Receive Queue
> memory scheme") introduced an undefined behaviour below due to
> "frag->last_in_page" is only initialized in
> mlx5e_init_frags_partition() when,
> 
> if (next_frag.offset + frag_info[f].frag_stride > PAGE_SIZE)
> 
> or after bailed out the loop,
> 
> for (i = 0; i < mlx5_wq_cyc_get_size(&rq->wqe.wq); i++)
> 
> As the result, there could be some "frag" have uninitialized
> value of "last_in_page".
> 
> Later, get_frag() obtains those "frag" and check "rag->last_in_page" in
> mlx5e_put_rx_frag() and triggers the error during boot. Fix it by always
> initializing "frag->last_in_page" to "false" in
> mlx5e_init_frags_partition().
> 
> UBSAN: Undefined behaviour in
> drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:325:12
> load of value 170 is not a valid value for type 'bool' (aka '_Bool')
> Call trace:
>   dump_backtrace+0x0/0x264
>   show_stack+0x20/0x2c
>   dump_stack+0xb0/0x104
>   __ubsan_handle_load_invalid_value+0x104/0x128
>   mlx5e_handle_rx_cqe+0x8e8/0x12cc [mlx5_core]
>   mlx5e_poll_rx_cq+0xca8/0x1a94 [mlx5_core]
>   mlx5e_napi_poll+0x17c/0xa30 [mlx5_core]
>   net_rx_action+0x248/0x940
>   __do_softirq+0x350/0x7b8
>   irq_exit+0x200/0x26c
>   __handle_domain_irq+0xc8/0x128
>   gic_handle_irq+0x138/0x228
>   el1_irq+0xb8/0x140
>   arch_cpu_idle+0x1a4/0x348
>   do_idle+0x114/0x1b0
>   cpu_startup_entry+0x24/0x28
>   rest_init+0x1ac/0x1dc
>   arch_call_rest_init+0x10/0x18
>   start_kernel+0x4d4/0x57c
> 
> Fixes: 069d11465a80 ("net/mlx5e: RX, Enhance legacy Receive Queue memory scheme")
> Signed-off-by: Qian Cai <cai@lca.pw>
> ---
>   drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> index 47eea6b3a1c3..96f5110a9b43 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> @@ -336,6 +336,7 @@ static void mlx5e_init_frags_partition(struct mlx5e_rq *rq)
>   
>   	next_frag.di = &rq->wqe.di[0];
>   	next_frag.offset = 0;
> +	next_frag.last_in_page = false;
>   	prev = NULL;
>   
>   	for (i = 0; i < mlx5_wq_cyc_get_size(&rq->wqe.wq); i++) {
> 

Thanks Qian.
Please zero-init the whole struct instead:

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c 
b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 1f433a06e637..55f4f5cc1d8f 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -312,11 +312,10 @@ static inline u64 mlx5e_get_mpwqe_offset(struct 
mlx5e_rq *rq, u16 wqe_ix)

  static void mlx5e_init_frags_partition(struct mlx5e_rq *rq)
  {
-       struct mlx5e_wqe_frag_info next_frag, *prev;
+       struct mlx5e_wqe_frag_info next_frag = {}, *prev;
         int i;

         next_frag.di = &rq->wqe.di[0];
-       next_frag.offset = 0;
         prev = NULL;

         for (i = 0; i < mlx5_wq_cyc_get_size(&rq->wqe.wq); i++) {


Thanks,
Tariq